This project proposes to study symbol mapping strategies of individuals with severe intellectual disabilities. Mental-age (MA) matched children without disabilities will also be studied to provide a basis for comparison. The main focus is the phenomenon of emergent mapping of underfine symbols with formerly undefined objects or other environmental events. The phenomenon may be seen under the following conditions: A subject views a stimulus array of two or more elements, one of which has not yet been defined in relation to a symbol (e.g., a dictated or printed word); the other element(s) have been so defined. If a novel, underfined symbol is presented, the subject is highly likely to relate it with the undefined element in this original mapping context and perhaps in other contexts thereafter. This phenomenon has been studied by those interested in a variety of issues in experimental, comparative, and developmental psychology. Despite the widespread interest, however, certain fundamental questions remain to be answered. First, on what bases do subjects relate undefined elements with undefined symbols? Is there a single, predominant strategy used by all subjects or do different subjects use different strategies? Second, under what conditions does EM result in symbol:element relations that are maintained outside of the original mapping context? When a relation is not maintained, does this outcome depend on the strategy operative in that content or to some other variable, perhaps a more general problem of observing or remembering? Third, can behavioral analysis identify specific behavioral prerequisites that are lacking when mapping relations are not maintained? Will training successfully establish these prerequisites? Fourth, are procedures that foster EM preferable to other approaches for teaching symbol:element relations to individuals with severe disabilities. Fifth, can responses in EM situations be related to subjects variables such as MA or other indicators of developmental status? The project Specific Aims are to: (1) apply novel matching to sample methods to analyze the stimulus control bases of the EM phenomenon in individuals with severe intellectual disabilities of two functional levels and MA-matched contrast subjects; (2) determine whether variations in intraexperimental history will alter the EM outcome in ways that will help to clarify its underlying behavioral processes; (3) examine procedure variables that may enhance the effectiveness of training procedure that make use of the EM phenomenon; (4) compare such training procedures with others that are typically used to teach conditional discriminations to individual with severe intellectual disabilities; (5) determine whether individuals who initially show poor learning outcomes after EM training will show improvements as they master an increasingly large baseline of conditional discriminations.